1. Field of the Invention
The present invention relates generally to dental models and more particularly to a novel model having a single, elongate, tapered pin that extends longitudinally through the base of the model beneath the teeth impressions of the model, whereby the pin can be removed from the model so that the model can be cut into isolated sections, and the sections can then be reassembled on the pin in their exact, precise relationship as in the model prior to cutting of the isolated sections. The present invention further relates to a method of making the novel dental model and to a novel articulation system for use with models of lower and upper teeth of a person's jaw.
2. State of the Art
In order to fabricate a dental prosthetic, such as a crown, inlay, bridge etc., a negative impression of a patient's mouth is taken using an impression material, and a reproduction of the impression is made as a model in the dental laboratory. Since the reproduction is a solid, positive model of the gums and at least several adjacent teeth in the mouth, it is necessary to isolate reproductions or dies of the individual tooth or teeth that have been prepared by the dentist to receive a restorative prosthetic.
The isolation of the desired tooth or teeth in the model is generally accomplished by sawing or cutting the solid, cast model into separate parts, i.e., the dies, with a separate die being cut for each tooth that is to receive a restorative prosthetic. Each desired die then consists of an isolated tooth of the model. Typically, the model will contain at least about 3 teeth, and cuts are made so as to isolate at least one of the teeth from the others.
It is essential during the construction of the prosthetic to reassemble the teeth dies back into the original model. When reassembled, the teeth must be located in as true as possible relationship to each other in the reassembled model as they were in the original, uncut model. To accomplish this, the methods used in the prior art have involved a time consuming operation wherein the tooth die is cut so as to be removed from the base stone, with the base stone remaining in a single, uncut condition. Means are then provided for repositioning the cut tooth die back on the base stone in as nearly as possible true relationship to its original position.
In one method called the grid method, the dental casting material forming the model is poured into a grid box combined with the negative mold of the person's teeth and gums. The model is cut to form the separate teeth sections or dies, and the dies can then be repositioned on the grid. This method has the serious disadvantage that getting the dies to relocate to precise position is difficult and time consuming because of debris lodging in the grids.
Several methods have been used in the prior art that utilize various types of dowel pins, each of which is secured to an individual die, for relocating the die back on the base stone. The methods of securing the dowel pins to the individual tooth die have been complicated and labor intensive. In one method, a dowel pin is incorporated into the cast material of the dental model in such a manner that when the tooth die is cut, the dowel pin remains in the tooth die and leaves a receptacle in the base stone so that the die can be reassembled to the base stone by inserting the projecting portion of the dowel pin of the tooth die into the respective receptacle in the base stone. In a second method, the entire, solid, dental model is first made and then holes are drilled above the individual prepared tooth areas or dies to receive individual dowel pins which are inserted and glued into the drilled holes. In either method, the dowel pins allow the tooth die to be removed from the mold and then relocated in the mold.
The dowels have in the past been shaped to alleviate rotational movement of the die relative to the axis of the dowel when the dowel is inserted into the receptacle in the base stone. However, precautions must still be rigidly adhered to in using the dental models having dies incorporating individual dowels. Rotation of the die relative to the dowel must be avoided. In addition, movement of the die in a fulcrum or pivoting effect, as well as up and down movement, must carefully be guarded against. Another serious disadvantage involves the extensive labor required in making the models utilizing a dowel for each individual die. It would be highly desirable to provide a dental model system that does not require a dowel pin for each removable tooth die, and that does not require excessive labor to make the model. There is a long felt need for a model in which the dies can be quickly and easily removed from the model and then just as quickly and easily reassembled into exact, precise relocation relative to the other teeth of the model, with no special precautions needed to prevent undesired movement of the individual dies in the reassembled mold.